Leak Before You Leap

Saturday, February 01, 1997
The squirrel tree frog, or Hyla squirella, lives in coastal forests from North Carolina to Texas and works hard to conserve what meager supplies of water it can scrounge during the arid southern autumn. To avoid drying out and dying, the inch-and-a-quarter-long frog descends from the trees at night to bathe its body in dew and moist soil, absorbing water through its skin and storing it as urine. Oddly though, when threatened by a predator such as an amphibian-collecting academic--and presumably more common antagonists like snakes--the frog urinates, jettisoning its valuable water supply before springing away. Water is a precious resource, so why void the bladder? asks Bryant Buchanan, a behavioral ecologist at the University of Missouri. Buchanan and grad student Ryan Taylor at Florida International University have found an explanation: by urinating, the frog becomes lighter and can jump farther. In lab tests, they found that a frog that urinated before it leaped jumped at least two body lengths farther than a frog that did not. The distance record--held by an unbloated frog-- is 20 body lengths.
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